US2035547A - Petroleum refining system - Google Patents

Description

W. T. HANCOCK PETROLEUM REFINING SYSTEM March 31, 1936.

- 2 Sheets-Sheet 1 Original Filed June 29, 1932 William ZJfancoclz I MW Inventor March 31, 1936. w N K 2,035,547

PETROLEUM REFINING SYSTEM Original Filed June 29, 1932 2 SheetsSheet 2 Z 45 45 "WW/W Patented Mar. 31, 19 36 UNITED STATES PATENT OFFICE Original application June 29, 1932, Serial No. 619,901. Divided and this application July 3,

1934, Serial No. 733,596

2 Claims.

This invention deals generally with petroleum refining systems, the present application being divisional of my copending application on Petrobeing at a temperature below that at which sub-- stantial cracking of the charging stock will occur, and the second heating stage being carried out at cracking temperatures which convert heavier fractions not vaporized in the first heating stage, to gasoline. The vapors from both heating stages are combined and subjected to fractionation for the recovery of gasoline. I then subject the condensate from the last mentioned fractionating operation to cracking, in order to convert to gasoline such heavier-than-gasoline fractions as kerosene and gas oil. Preferably the vapors from this final cracking stage are combined with the previously combined vapors produced during the above mentioned heating stages. For the purpose of rendering the product gasoline nondetonating to a high degree, the vapors are treated in certain stages of the process, as later described, with adsorptlve clay such as fullers earth or other well known substances possessing similar adsorptive properties.

The invention further contemplates a novel method of combining with a residuum carrying suspended carbon particles, an oil derived from an extraneous source, and preferably a carbon free oil lighter than the residuum, for the purpose of facilitating the discharge of carbon particles from a chamber into which the residuum is delivered, and for the additive purpose of sufiiciently diluting the residuum to render it suitable for use as fuel oil.

The various features and objects of the invention will be understood to best advantage without necessity for further preliminary discussion, from the following description. I have shown in the drawings and in diagrammatic form, certain apparatus suitable for carrying out the process, but with the understanding that the process is not necessarily limited to the use of any particular type of equipment, and that those familiar with the art will recognize the adaptability of various known arrangements and constructions of apparatus for carrying out the process.

Reference is had throughout the following description to the accompanying drawings, in which:

to partial vaporization, in accordance with its Fig. 1 is a general view illustrating a typical petroleum refining system embodying the invention, the apparatus being shown diagrammatically and in flow sheet form;

Fig. 2 is an enlarged sectional view of the clay tube cracking still indicated at S in Fig. 1;

Fig. 3 is an enlarged sectional view of the separator shown at D in Fig. 1; and

Fig. 4 is a section on line 4-4 of Fig. 3.

Referring first to Fig. 1, the charging stock or oil to be subjected to distillation and cracking, may be derived from any suitable source, as supply tank l0, and may be of any suitable character or constituency for distillation under the conditions hereinafter described. For example, the system has been found to operate satisfactorily and efilciently on charging stock consisting of residuum from straight run distillation, that is, the residual content of the crude after the gasoline or lighter fractions have been removed in topping stills. From supply source II), the oil is taken by line i I to pipe still l2, in passing through the coils of which the oil is subjected to a first stage heating tov an outlet temperature between substantially 500 F. to 700 F. andpreferably, where charging stock consisting of straight run residuum is being used, to. a' temperature of about 600 F.

In this first heating stage, the oil is subjected volatile content, and is then discharged through line l3 into a separating chamber ,see Fig. 3, within the lower interior of shell l5. As illustrated most clearly in Fig. 4, line l3 connects tangentially with shell l5 at an upper point in separating chamber l4, line l3 communicating with the interior of the shell by way of a comparatively narrow and vertically extending slot IS. The vapor and residuum mixture is thus discharged tangentially into and in a circular swirling path within the separating chamber, the heavy unvaporized residual bodies being thrown to the outside of the swirling mixture and caused to drain down along the wall of the shell. The vapors are released toward the center of the chamber to pass upwardly through the bubble cap section I l of the separator, as will be presently described.

An oil, such as fuel oil, derived from a suitable extraneous source, is also discharged into the separating chamber in such manner as to follow the circular path being taken by the residual oil from line I3. A two-fold purpose is accomplished by injecting fuel oil into the separating chamber. First, the fuel oil, in being intimatelyv 55 tarrybodiesthat maybepresent therein, to pre-'-.

vent the deposit and accumulation of such bodies on the wall and in the bottom of shell I. This diluting and carbon removing eil'ect accomplished by the injection of a carbon free oil into the separating chamber, applies also to the cracking still residuum injected into the separating chamber, as later described. The fuel oil also serves to dilute the heavy residuums injected into the separating chamber, toan extent such as to render them suitable for use as fuel oil.

The fuel oil is injected into theiseparating chamber from tangential line it through a slotted orifice I! in the wall of the shell, the inected fuel oil following a circular path in conformity with the wall of the shell and in the same direction as the path followed by the injectedresidual oils. The residuum and fuel oil mixture is drained from the separating chamber through line and thence to a fuel oil tank. not shown.

I preferably .provide within the upper interior of the separator shell, a series of bubble cap trays ll of conventional design well known to those familiar with the art. In passing upwardly through the bubble cap trays, the vapors released in the separating chamber are stripped of whatever liquid or solid particles they may contain, so that when discharged through line 22, thevapors are free from all contaminating bodies of a heavy nature. In a typical instance, the vapors taken from the separator may be said to consist mainly of fractions including, and lighter than gas oil, although the vapor constituency may vary in accordance with such factors as the nature of the charging stock, the temperature at which the first heating stage is conducted, and the extent of condensation in the separator.

The vapors "passrfrom the separator through line 22 to a fractionating column 23, which may be of any suitable design, for example of the multiple bubble cap plate type.. Within the fractionating column, the vapors become depleted of their heavier constituents to the extent that the vapors through outlet line 24 consist mainly of gasoline, kerosene, and perhaps some part of the gas oil fraction. The vapors are passed through a clay tower 25 which preferably is of the type disclosed in my copending application on' Distillation system, Ser. No. 608,755, filed May 2, '1932. The clay tower may be stated briefly to comprise a vertically extending shell 26 containing a body of adsorbent clay 21, such as fuller's earth or the like, the vapors being passed upwardly through the clay to be discharged through line 20. While numerous advantages are gained with respect to the properties of the finished gasoline as a result of passing the vapors through a body of adsorbent clay, such as a material reduction in the amount of acid usually required for treatment, and in giving to the product a substantially water-like color without further treatment, the principal object of so treating the vapors is to increase the non-detonating properties of the final product, and to increase the so called octane number of the gasoline. The effect had upon the product, as regards rendering it non-detonating as a result of the vapor treatment by adsorbent clay, is more fully treated in the copending application to which I have reerred.

stage.

From the clay tower, the vapors are taken through line 20 to fractionating column ll. wherein all constituents heavier than gasoline are removed. The gasoline vapors are thence passed through line ii to final condenser 32, and

the condensed heavy constituents are led off from the fractionating column throughline a. Preferably the system up to fractionating column 30 is maintained under a substantial pressure, and for this purpose a pressure control valve 84 is placed in line 20, the valve being set ,to maintain a back pressure within the heating units, separator D, fractionating column 22 and the clay tower 25, in the neighborhood of 100 pounds per square inch gage. The residuum or condensate from fractionating column 23 is conducted through line to a second stage heating tube still 38, the- 011' being forced through under pressure by pump 31, and the oil being heated in passing through the still to a temperature between 800 F. and 1100 F. Where straight run residuum is being used as charging stock, the oil outlet temperature in the still 36 may be in the neighborhood of 900 F. Under the temperatures and pressures prevailing in the second stage heater 36, the oil is subjected to cracking to convert a large proportion of the residuum being fed to the cracking still, and consisting of kerosene, gas oil and heavier fractions, to fractions coming within the gasoline range.

The mixture of vapors and unvaporized residuum is discharged from the cracking still through line 38 into separator chamber l4, line 38 connecting with the separator shell at a tangent, and the mixture of cracked vapors and residuum being injected into the chamber through a slotted orifice 39, in a manner similar to the injection of the oil and vapor mixture from the first stage heater, as previously described. The cracked vapors combine, in the separating chamber, with those produced from the first heating The second stage is combined with the first stage residuum and with the oil introduced through line I8, to be discharged by way of line 20 for use as fuel oil, or for any other desired purpose.-

In order that a maximum production of gasoline may be had from the available constituents of the charging stock capable of conversion to gasoline, the bottoms from fractionating column 30 also are preferably subjected to cracking and conversion to gasoline. Although this final cracking operation may be carried out according to any desired process, within the broad aspects of the invention, I preferably adopt, for this purpose, a cracking system of the character hereinafter described, and which I believe to be an inventive departure from cracking systems heretofore developed. This cracking system may be characterized as providing for the cracking of the vaporized oil in the presence of an adsorptive clay. It has been common practice heretofore to treat oil vapors with adsorbent clay for the purpose of removing undesirable heavy constituents, as by the formation of heavy, dark colored polymers induced by the adsorptive properties of the clay, but to my knowledge it has not been to subject the vapors to cracking in the presence of adsorptive clays. Heretofore, the vapors have been passed through clay at substantially the vaporizing temperature of the oil, and perhaps in certain instances at temperatures slightly above, but in no instance have the vapors been contacted with the clay at high cracking tempera, tures, say in the neighborhood of 1000 1".

Thebottoms i'romtractionatingcolumn ll pass through line it to pipe still 4! in which'the oil is completely vaporized by heating to a temperature in the neighborhood of 500' I or higher, in accordance with the character of the heavy constituents in the oil. At a temperature of about 500" F., of course. the vapors will not be subjected to substantial cracking. The vapors thence are taken by way of line ll to the clay tube cracking still 8. Asshown in Fig. 2, still 8 comprises a brick work 42 within which a series of horizontally extending tubes 43 are arranged, the ends oi the tubes being connected by return bends 44. Any suitable number of these tubes 43' may be used to aiford the necessary length of traveloi the vapors at cracking temperatures in contact with the clay, three tubes being shown herein as typical only. Tubes 43 are filled with a suitable adsorbent clay 45, such as iullers earth .or the like, such clay, by virtue of its adsorbent nature, having the property, when in the presence of oil vapors at cracking temperatures, of rendering the gasoline product resulting from the cracking operation, highly non-detonating and capable of being brought within 'motor fuel specification with a slight acid treatment. Cracking the vapors in the presence of adsorbent clay results also in the rendering of gasoline product superior in color. In fact, it is unnecessary in the cracking oi many oils by this method, for the gasoline product to be given final acid or clay treatment to meet the usual color requirements.

In passing through the clay containing tubes of the cracking still S, the vapors are heated to temperatures within substantially the range oi. 800 F. to 1200" F. and preferably at about atmospheric pressure, although some substantial pressure 'may be maintained on the vapors if desired. The cracked vapors pass from the still 8 through line 31 and may be taken by way of line 48 to suitable iractionating apparatus, not shown, for the recovery of gasoline, or the cracked vapors may be returned through line 49 to fractionating tower 23 to be combined with the previously combined vapors from the first and second heating stages, being passed into tower 23.

Since the latter is operating under a pressure I tangential direction at such high velocity as to cause said residual oil to follow the wall of the chamber in a downwardly spiraling path, injecting a stream of oil from an extraneous source tangentially into said chamber in said direction and at suflicient velocity that the oil spirals down along the wall of the chamber, both said streams being injected into said chamber a substantial distance above the bottom thereof and caused to intimately commingle and flow downwardly together about a central vertically extending zone into which vapors are liberated from said residual oil.

2. The method of refining petroleum 'oils' that includes, heating the oil to cracking temperatures to produce a stream of cracked vapors and residual oil containing solid carbon particles, injecting said stream into a cylindric chamber in a tangential direction at such high velocity as to cause said residual oil to follow the wall of the chamber in a downwardly spiraling path, injecting a stream of lighter and substantially carbon iree'oil from an extraneous source tangentially into said chamber. in said direction and at sufflcient velocity that the oil spirals down along the wall of the chamber, both said streams being injected into said chamber a substantial distance above the bottom thereof and caused to intimately commingle and flow downwardly together about a central vertically extending zone into which vapors are liberated from said residual oil.

WILLIAM T. HANCOCK.

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